Unpredictable what derive attributes allow only literals vs expressions

[epage]

Please complete the following tasks

• I have searched the discussions
• I have searched the existing issues

Rust Version

rustc 1.55.0 (c8dfcfe04 2021-09-06)

Clap Version

v3.0.0-beta.4

Minimal reproducible code

N/A

Steps to reproduce the bug with the above code

Use various attributes without reading the code or documentation

Actual Behaviour

Some will work as literals while others allow any expression

Expected Behaviour

Be consistent. Solving this through documentation will lead to either

• Users consulting the documentation on each attribute
• Users keep trying to do things and fail
• Users using a "safe" subset of the API that avoids the above two

Additional Context

No response

Debug Output

No response

[epage]

I think #3452 ended up fixing this.